Gadolinium-based contrast agents are commonly used to improve visibility of internal structures when a patient undergoes magnetic resonance imaging (MRI). These agents are typically administered intravenously immediately prior to imaging. Many contrast agents used in MRI cause toxicity in various areas of the body if they are not excreted rapidly by the kidney. These include for example, chelated organic gadolinium compounds which are not nephrotoxic in themselves, but which if retained in the body for extended periods of time release gadolinium ions which are toxic to various organs and cells of the body including skin, nerves, etc. The problems particularly occur in patients who are at risk for reduced kidney function. Serious diseases including nephrogenic systemic fibrosis (NSF) are among the consequences of this problem. (see, for example, Briguori et al., Catheter Cardiovasc. Intery (2006) 67(2): 175-80; Grobner et al., Kidney Int. (2007) 72(3): 260-4; Nortier et al., Nephrol. Dial. Transplant (2007) 22(11): 3097-101).
The FDA requested a boxed warning for contrast agents used to improve MRI images on May 23, 2007 stating that patients with severe kidney insufficiency who receive gadolinium-based agents are at risk for developing NSF, a debilitating and potentially fatal disease. In addition, patients just before or just after liver transplantation, or those with chronic liver disease, are also at risk for developing NSF if they are experiencing kidney insufficiency of any severity. The boxed warning is now included in each of the five gadolinium-based contrast agents currently approved for use in the United States. Thus, a need exists to reduce the toxicity that is caused by contrast agents in patients with risk factors for compromised renal function.